We have 10000 completed instances of process model version 80.0, which has custo

I can't make any recommendations on how to use the process upgrade API, as I haven't had cause to use it. I don't know what your use-case is, but it seems to me like you could benefit from switching to an entity-backed record design. If you already have a CDT that is linked to a data entity, you can easily make a record from the data entity. Tempo reports can be created off this with queryrecord (or queryentity, if you don't want to create a record, listview, and dashboard). This would allow you to no longer need to deal with the memory requirements and hassle of maintaining 10,000 process instances, which it sounds like you are using for reporting and possible process instance dashboards.

I can't make any recommendations on how to use the process upgrade API, as I haven't had cause to use it. I don't know what your use-case is, but it seems to me like you could benefit from switching to an entity-backed record design. If you already have a CDT that is linked to a data entity, you can easily make a record from the data entity. Tempo reports can be created off this with queryrecord (or queryentity, if you don't want to create a record, listview, and dashboard). This would allow you to no longer need to deal with the memory requirements and hassle of maintaining 10,000 process instances, which it sounds like you are using for reporting and possible process instance dashboards.